Ball grid array package fabrication with IC die support structures

ABSTRACT

A system and method of assembling a ball grid array (BGA) package with IC die support is described. A stiffener is attached to a substrate that includes a centrally located opening with an integrated circuit (IC) die support structure removably held therein. An IC die is mounted to a central region of the stiffener. Further assembly process steps may be performed on the BGA package with IC die support. The IC die support structure is removed from the centrally located opening. In aspects of the invention, the IC die support structure is removably held in the opening by an adhesive tape or by one or more substrate tabs.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/352,877, filed Feb. 1, 2002 (Atty. Dkt. No.1875.0200002), which is herein incorporated by reference in itsentirety.

[0002] The following applications of common assignee are related to thepresent application, have the same filing date as the presentapplication, and are herein incorporated by reference in theirentireties:

[0003] “Ball Grid Array Package Enhanced with a Thermal and ElectricalConnector,” Atty. Dkt. No. 1875.0200004, Ser. No. ______;

[0004] “Ball Grid Array Package with Patterned Stiffener Layer,” Atty.Dkt. No. 1875.0200005, Ser. No. ______;

[0005] “Ball Grid Array Package with Stepped Stiffener Layer,” Atty.Dkt. No. 1875.2730000, Ser. No. ______;

[0006] “Ball Grid Array Package with Multiple Interposers,” Atty. Dkt.No. 1875.2750000, Ser. No. ______; and

[0007] “Ball Grid Array Package with Separated Stiffener Layer,” Atty.Dkt. No. 1875.2760000, Ser. No. ______.

BACKGROUND OF THE INVENTION

[0008] 1. Field of the Invention

[0009] The invention relates generally to the field of integratedcircuit (IC) device packaging technology and, more particularly, totechniques for providing support to a ball grid array (BGA) packagesduring assembly processes.

[0010] 2. Background Art

[0011] Integrated circuit (IC) dies are typically mounted in or on apackage that facilitates attachment to a printed circuit board (PCB).One such type of IC die package is a ball grid array (BGA) package. BGApackages provide for smaller footprints than many other packagesolutions available today. A BGA package has an array of solder ballslocated on a bottom external surface of a package substrate. The solderballs are reflowed to attach the package to the PCB. In one type of BGApackage, the IC die is mounted to a top surface of the packagesubstrate. Wire bonds typically couple signals in the IC die to thesubstrate. The substrate has internal routing which electrically couplesthe IC die signals to the solder balls on the bottom substrate surface.

[0012] A number of BGA package substrate types exist, including ceramic,plastic, and tape (also known as “flex”). In some BGA package types, astiffener may be attached to the substrate to supply planarity andrigidity to the package. In such packages, the IC die may be mounted tothe stiffener instead of the substrate. Openings in the stiffener may beused to allow the IC die to be wire-bonded to the substrate.

[0013] Die-up and die-down BGA package configurations exist. In die-upBGA packages, the IC die is mounted on a top surface of the package,opposite of the side to which the solder balls are attached. In die-downBGA packages, the IC die is mounted on a bottom surface of the package,on the same side as which the solder balls are attached.

[0014] Various assembly process steps for the BGA package may causeharmful stresses and shocks to the IC die. These process steps includeattachment of the IC die to the BGA package, attachment of wire bonds,encapsulation of the IC die and wire bonds for environmental protection,attachment of solder balls to the BGA package, and other steps. As aresult of the stress occurring during these processes, the packagestiffener may become deformed. The deformation of the stiffener may leadto the formation of cracks in the IC die, potentially rendering the ICdie inoperable. Hence, costs in terms of lost money and time may beincurred for repairing and replacing damaged IC dies and BGA packages,among other costs.

[0015] Hence, what is needed are improved BGA package assembly processesthat reduce stresses and shocks that may harm the BGA package.

BRIEF SUMMARY OF THE INVENTION

[0016] Ball grid array (BGA) packages having enhanced electrical,thermal, and mechanical characteristics are described herein. Inparticular, improved assembly processes and structures are described. Inan aspect of the present invention, a system and method of assembling aBGA package with integrated circuit (IC) die support are described. Astiffener is attached to a substrate that includes a centrally locatedopening with an IC die support structure removably held therein. An ICdie is mounted to a central region of the stiffener. The IC die supportstructure is subsequently removed from the centrally located opening.

[0017] In a further aspect, additional assembly process steps inaddition to mounting the IC die are performed before removing the IC diesupport structure. Such additional steps include, for example,connecting a bond pad of the IC die to a contact pad on the substratewith a wire bond. In another aspect, the IC die is encapsulated on thestiffener. The IC die support structure supports the stiffener duringone or more of these assembly process steps to reduce deformation of thestiffener and damage to the IC die.

[0018] In an aspect of the present invention, the IC die supportstructure is attached to the substrate by an adhesive tape. The adhesivetape to which the IC die support structure is attached removably holdsthe IC die support structure within the centrally located opening. Theapplied adhesive tape is detached from the substrate to remove the ICdie support structure from the centrally located opening.

[0019] In another aspect of the present invention, the IC die supportstructure is formed in the opening as a portion of the substrate. The ICdie support structure portion of the substrate remains removably held inthe opening by one or more substrate tabs. The one or more substratetabs are broken to release the IC die support structure from thecentrally located opening.

[0020] In another aspect of the present invention, a system and methodof assembling a plurality of BGA packages is described. A substratestrip that includes a plurality of substrates that each include acentrally located opening with an IC die support structure removablyheld therein is formed. A stiffener strip that includes a plurality ofstiffeners is attached to the substrate strip such that a first surfaceof each stiffener of the plurality of stiffeners is attached to a firstsurface of a corresponding substrate of the plurality of substrates. AnIC die is mounted to a central region of a second surface of eachstiffener of the plurality of stiffeners. A bond pad of the IC diemounted to each stiffener of the plurality of stiffeners is connected toa contact pad on the first surface of the corresponding substrate of theplurality of substrates with a wire bond. The IC die and the wire bondare encapsulated on the second surface of each stiffener of theplurality of stiffeners. The IC die support structure is subsequentlyremoved from the centrally located opening of each substrate of theplurality of substrates.

[0021] Further aspects, features, and advantages of the presentinvention, as well as the structure and operation of the variousembodiments of the present invention, are described in detail below withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0022] The accompanying drawings, which are incorporated herein and forma part of the specification, illustrate the present invention and,together with the description, further serve to explain the principlesof the invention and to enable a person skilled in the pertinent art tomake and use the invention.

[0023]FIGS. 1A and 1B illustrate cross-sectional views of flex BGApackages.

[0024]FIG. 2A shows a top view of a stiffener.

[0025]FIG. 2B shows a temperature distribution for a stiffener duringoperation of an IC device in a flex BGA package.

[0026]FIG. 2C shows a top view of an alternative stiffenerconfiguration.

[0027]FIG. 3 shows a cross-sectional view of a die-up plastic BGApackage.

[0028]FIG. 4A illustrates a cross-sectional view of a die-up BGApackage.

[0029]FIGS. 4B and 4C illustrate exemplary solder ball arrangements forthe die-up BGA package of FIG. 4A.

[0030]FIG. 5 shows exemplary routing in a substrate layer.

[0031]FIG. 6 shows an example BGA package with a heat spreader attachedto the package stiffener through an opening in the package substrate.

[0032]FIG. 7 shows an example view of the bottom surface of the BGApackage of FIG. 6.

[0033]FIG. 8 shows an example panel of stiffeners, according to anembodiment of the present invention.

[0034]FIG. 9 shows an example panel of substrates, according to anembodiment of the present invention.

[0035]FIG. 10A shows an example cross-sectional view of an IC die beingmounted to a stiffener during an assembly process for a BGA package.

[0036]FIG. 10B shows a cross-sectional view illustrating example stressand deformation of elements of the BGA package resulting from the IC diebeing mounted to the stiffener during the assembly process for the BGApackage shown in FIG. 10A.

[0037]FIG. 10C shows a cross-sectional view illustrating example stressand deformation of elements of a BGA package resulting from a wire bondbeing attached to an IC die during an assembly process for the BGApackage.

[0038]FIG. 11 illustrates a cross-sectional view of an example IC diesupport structure that at least partially relieves the stress anddeformation of elements of the BGA package shown in FIG. 10B, accordingto an embodiment of the present invention.

[0039]FIG. 12 illustrates a bottom view of a substrate with an exampletape-supported IC die support structure, according to an embodiment ofthe present invention.

[0040] FIGS. 13-15 illustrate bottom and/or top views of substrates withtab-attached IC die support structures, according to embodiments of thepresent invention.

[0041]FIG. 16 shows a flowchart providing example steps for assembling aBGA package with IC die support, according to embodiments of the presentinvention.

[0042]FIGS. 17A and 17B show flowcharts providing example steps forassembling a plurality of BGA packages, according to embodiments of thepresent invention.

[0043] The present invention will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers indicateidentical or functionally similar elements. Additionally, the left-mostdigit(s) of a reference number identifies the drawing in which thereference number first appears.

DETAILED DESCRIPTION OF THE INVENTION

[0044] Overview

[0045] The present invention is directed to a method and system forimproving assembly processes for BGA packages, and therefore toimproving the mechanical, thermal, and electrical performance of BGApackages. The present invention is applicable BGA packages of all typesof BGA substrates, including ceramic, plastic, and tape (flex)substrates. Furthermore the present invention is applicable to die-up(cavity-up) and die-down (cavity-down) orientations.

[0046] Numerous embodiments of the present invention are presentedherein. First, ball grid array package types are described below. Next,further detail on the above described embodiments for assembling BGApackages with IC die support, and additional embodiments according tothe present invention, are described. The embodiments described hereinmay be combined as required by a particular application.

[0047] Ball Grid Array (BGA) Package

[0048] A ball grid array (BGA) package is used to package and interfacean IC die with a printed circuit board (PCB). BGA packages may be usedwith any type of IC die, and are particularly useful for high speed ICs.In a BGA package, solder pads do not just surround the packageperiphery, as in chip carrier type packages, but cover most or all ofthe bottom package surface in an array configuration. BGA packages arealso referred to as pad array carrier (PAC), pad array, land grid array,and pad-grid array packages. BGA packages types are further described inthe following paragraphs. For additional description on BGA packages,refer to Lau, J. H., Ball Grid Array Technology, McGraw-Hill, New York,(1995), which is herein incorporated by reference in its entirety.

[0049] Die-up and die-down BGA package configurations exist. In die-upBGA packages, the IC die is mounted on a top surface of the substrate orstiffener, in a direction away from the PCB. In die-down BGA packages,the IC die is mounted on a bottom surface of the substrate or stiffener,in a direction towards the PCB.

[0050] A number of BGA package substrate types exist, including ceramic,plastic (PBGA), and tape (also known as “flex”) (for example, refer toHayden, T. F., et al., Thermal & Electrical Performance and ReliabilityResultsfor Cavity-Up Enhanced BGAs, Electronic Components and TechnologyConference, IEEE, pp. 638-644 (1999), which is incorporated herein byreference). FIG. 1A illustrates a flex BGA package 100. Flex BGA package100 includes an IC die 102, a tape substrate 104, a plurality of solderballs 106, and one or more wire bonds 108. Tape or flex BGA packages areparticularly appropriate for large IC dies with large numbers of inputsand outputs, such as application specific integrated circuits (ASIC) andmicroprocessors.

[0051] Tape substrate 104 is generally made from one or more conductivelayers bonded with a dielectric material. For instance, the dielectricmaterial may be made from various substances, such as polyimide tape.The conductive layers are typically made from a metal, or combination ofmetals, such as copper and aluminum. Trace or routing patterns are madein the conductive layer material. Substrate 104 may be a single-layertape, a two-layer tape, or additional layer tape substrate type. In atwo-layer tape, the metal layers sandwich the dielectric layer, such asin a copper-Upilex-copper arrangement.

[0052] IC die 102 is attached directly to substrate 104, for example, byan epoxy. IC die 102 is any type of semiconductor IC.

[0053] One or more wire bonds 108 connect corresponding bond pads 118 onIC die 102 to contact pads or points 120 on substrate 104.

[0054] An encapsulate 116, such as a mold compound, epoxy, or otherencapsulating material, covers IC die 102 and wire bonds 108 formechanical and environmental protection.

[0055] As shown in FIG. 1A, flex BGA package 100 does not include astiffener. In some BGA package types, particularly in flex BGA packages,a stiffener can be attached to the substrate to add planarity andrigidity to the package. FIG. 1B illustrates a flex BGA package 110,similar to flex BGA package 100, that incorporates a stiffener 112.Stiffener 112 may be laminated or otherwise attached to substrate 104.Stiffener 112 is typically made from a metal, or combination of metals,such as copper, tin, and aluminum, or may be made from a polymer andother materials, for example. Stiffener 112 also may act as a heat sink,and allow for greater heat spreading in BGA package 110. One or moreopenings 114 in stiffener 112 may be used to allow for wire bonds 108 toconnect IC die 102 to substrate 104. Stiffener 112 may be configured inother ways, and have different opening arrangements than shown in FIG.1B.

[0056] The use of a stiffener in a flex BGA package requires additionalconsiderations when attempting to manage heat spreading. FIG. 2A shows atop view of a stiffener 112. Stiffener 112 includes an opening 114adjacent to all four sides of an IC die mounting position 202 in thecenter of stiffener 112. FIG. 2B shows a temperature distribution 204 ofa stiffener, such as stiffener 112, during operation of an IC die in aflex BGA package. Temperature distribution 204 shows that heat transferfrom IC die mounting position 202 to the edges of stiffener 112 issubstantially limited by openings 114. Openings 114 act as thermalbarriers to heat spreading in stiffener 112.

[0057]FIG. 2C shows a top view of an alternative configuration forstiffener 112, according to an embodiment of the present invention.Stiffener 112 includes an opening 206 adjacent to all four sides of anIC die mounting position 202 in the center of stiffener 112. Openings206 are similar to openings 114 of FIG. 2A, but have a different shape.The different shape can enhance thermal transfer to the outer areas ofstiffener 112, for example. Further alternatively shaped openings instiffener 112 are applicable to the present invention, includingelliptical or rounded openings, etc.

[0058]FIG. 3 shows a cross-sectional view of a conventional die-up PBGApackage 300. PBGA package 300 includes a plastic substrate 302, an ICdie 304, a plurality of solder balls 306, a plurality of wire bonds 308,a die pad 310, one or more vias 314, and one or more thermal/ground vias316.

[0059] Plastic substrate 302 includes one or more metal layers formed onan organic substrate. For example, plastic or organic substrates mayinclude materials such as “BT”, which includes a resin calledbis-maleimide triazine, and/or “FR-4,” which is a fire-retardant epoxyresin-glass cloth laminate material, and/or other similar materials. ICdie 304 is mounted to die pad 310. IC die 304 may be attached to die pad310 with an epoxy, such as a silver-filled epoxy. Wire bonds 308 connectsignals of IC die 304 to substrate 302. For instance, gold bonding wireis bonded from aluminum bond pads on IC die 304 to gold-plated contactpads on substrate 302. The contact pads on substrate 302 connect tosolder balls 306 attached to the bottom surface of substrate 302,through vias 314 and routing within substrate 302 using copperconductors 312. Thermal/ground vias 316 connect die pad 310 to one ormore thermal/ground balls 322 on the center bottom surface of substrate302. An encapsulate, mold compound, or epoxy 320 covers IC die 304 andwire bonds 308 for mechanical and environmental protection.

[0060] As described above, a BGA package includes an array of solderballs located on a bottom external surface of the package substrate.FIG. 4A illustrates a cross-sectional view of a die-up BGA package 400.FIGS. 4B and 4C illustrate exemplary solder ball arrangements for die-upBGA package 400. As shown in FIG. 4A, BGA package 400 includes an IC die408 mounted on a substrate 412.

[0061] IC die 408 is electrically connected to substrate 412 by one ormore wire bonds 410. Wire bonds 410 are electrically connected to solderballs 406 underneath substrate 412 through corresponding vias androuting in substrate 412. The vias in substrate 412 can be filled with aconductive material, such as solder, to enhance these connections.Solder balls 406 are attached to substrate 412, and are used to attachthe BGA package to a PCB.

[0062] Note that although wire bonds, such as wire bonds 410, are shownand described herein, IC dies may be mounted and coupled to a substratewith solder balls located on the bottom surface of the IC die, by aprocess commonly referred to as “C4” or “flip chip” packaging.

[0063] As shown in FIG. 4B, solder balls 406 may be arranged in anarray. FIG. 4B shows a 14 by 14 array of solder balls on the bottomsurface of BGA package 400. Other sized arrays of solder balls are alsoapplicable to the present invention. Solder balls 406 are reflowed toattach BGA package 400 to a PCB. The PCB may include contact pads towhich solder balls 406 are bonded. PCB contact pads are generally madefrom a metal or combination of metals, such as copper, nickel, tin, andgold.

[0064]FIG. 4C shows a bottom view of BGA package 400, with analternative solder ball array arrangement. BGA package 400 attaches anarray of solder balls 406 on a bottom surface of substrate 412. As shownin FIG. 4C, solder balls 406 are located in a peripheral area of thebottom surface of substrate 412, away from a substrate center 424. Forexample, solder balls 406 on the bottom surface of substrate 412 may belocated outside an outer profile area of an IC die mounted on theopposite surface of substrate 412. The solder ball array may beorganized in any number of ways, according to the requirements of theparticular BGA package application.

[0065] The solder ball arrangement shown in FIG. 4C is particularlyapplicable to embodiments of the present invention described below, suchas for attaching a heat spreader/heat sink/heat slug/thermal connectorto a bottom surface of a BGA package. The heat spreader/heat sink/heatslug/thermal connector may be connected in substrate center 424, forexample.

[0066] For example, FIG. 6 shows a cross-sectional view of an exampleBGA package 600, with a heat spreader 602 attached to a bottom surface.As shown in FIG. 6, heat spreader 602 is attached to a bottom surface ofstiffener 112 through an opening 604 in substrate 104. FIG. 7 shows abottom view of BGA package 600, with heat spreader 602 attached tostiffener 112 through opening 604. Heat spreader 602 is attached tostiffener 112 by an adhesive material 610. Heat spreader 602 may be madefrom a metal, such as copper, aluminum, and additional metals andcombinations/alloys thereof. Furthermore, heat spreader 602 may be madeof other electrically and/or thermally conductive materials.

[0067] Heat spreader 602 is typically thermally conductive, andtherefore aids the transfer of heat generated during operation of IC die102 out of BGA package 600. Hence, heat spreader 602 may also bereferred to as a heat sink, a heat slug, and a thermal connector. Heatfrom IC die 102 is allowed to conduct through stiffener 112 to heatspreader 602. A bottom surface 606 of heat spreader 602 may be attachedto a printed circuit board (PCB), to transfer heat from heat spreader602 to the PCB. Heat spreader 602 may also be electrically conductive,and therefore may be used as a ground, power, or other signal plane forBGA package 600. One or more wire bonds 608 may couple these electricalsignals from IC die 102 to heat spreader 602.

[0068] As described above, the BGA package substrate provideselectrically conductive vias and routing on one or more electricallyconductive layers to connect contact pads for wire bonds on its uppersurface to solder balls attached to the bottom substrate surface. Forillustrative purposes, FIG. 5 shows solder ball pads and routing 504 inan example bottom substrate layer 502.

[0069] BGA packages according to the present invention may be assembledsingly, or may be assembled in quantities greater than one at a time.For example, FIG. 8 shows an example panel 800 of stiffeners 112,according to an embodiment of the present invention. FIG. 9 shows anexample panel 900 of substrates 104, according to an embodiment of thepresent invention. Panel 800 includes six stiffeners 112 a-112 f, andpanel 900 shows six substrates 104 a-104 f. Note that the presentinvention is applicable to panels having any number of stiffeners112/substrates 104 for assembling any number of BGA packages. As shownin FIG. 9, substrates 104 a-104 f each include a centrally locatedopening 604.

[0070] During an assembly process step for assembling a group of BGApackages, panel 900 is attached to panel 800 to form a combinedstiffener strip/substrate strip panel. Further assembly process stepsmay be directed to the combined stiffener strip/substrate strip panel,including, for example: (i) attachment of the IC die to eachstiffener/substrate combination in the combined panel, (ii) attachmentof wire bonds between the IC die and contact pads on the substrate foreach stiffener/substrate combination in the combined panel, (iii)encapsulation of the IC die and wire bonds for environmental protectionfor each stiffener/substrate combination in the combined panel, and/or(iv) attachment of solder balls to the substrate to eachstiffener/substrate combination in the combined panel.

[0071] The present invention is directed to reducing harm to IC dies andother BGA package elements during assembly process steps, and toimproving assembly process yields, for BGA packages produced singly orin a group. The present invention is also applicable to improvingthermal, mechanical, and electrical performance in the BGA package typesdescribed herein, and in other BGA package types.

[0072] Embodiments for Assembling BGA Packages with IC Die Support

[0073] According to embodiments of the present invention, enhancementsto an assembly or fabrication process for a BGA package are provided,through the introduction of IC die support structures. This sectionprovides embodiments and description of IC die support structures of thepresent invention. For illustrative purposes, the present invention isdescribed below in the context of elements of BGA packages 100 and 110of FIGS. 1A and 1B, but the present invention is not limited to theseexample BGA package types. The present invention is applicable to alltypes of BGA packages, including tape and plastic substrate packagessuch as BGA packages 100, 110, and 300 described above, ceramicsubstrate BGA packages, and other BGA package types.

[0074] During the assembly of BGA packages having an opening in thesubstrate, such as BGA package 600 shown in FIG. 6, the IC die canexperience harmful stresses and shocks. For example, FIG. 10A shows anexample cross-sectional view of a mounting process for an IC die 102. Asshown in FIG. 10A, stiffener 112 has been attached to substrate 104,which resides against a support surface 1000. Support surface 1000 mayor may not be present during assembly of the BGA package. During theassembly process portion shown in FIG. 10A, IC die 102 is being movedtoward the top surface of stiffener 112. FIG. 10B shows the IC die 102contacting the top surface of stiffener 112. Arrows 1002 represent adownward force being exerted on IC die 102 while being mounted tostiffener 112. For example, IC die 102 may be forced and held down onstiffener 112 for a period of time to allow an adhesive material toadhere IC die 102 to stiffener 112. Similar localized forces may also beapplied to bond pads on IC die 102 during BGA package assemblyprocesses, including attachment of wire bonds, such as is shown in FIG.10C.

[0075] A force being applied to mount IC die 102 to the top surface ofstiffener 112 can cause harm to stiffener 112. As shown in FIG. 10B,stiffener 112 has become deformed (e.g., curved) due to the appliedforce. As shown in FIG. 10C, attachment of a wire bond 108 to a bond padof IC die 102 can also deform stiffener 112. The resulting curvature maybe temporary or permanent. The outer edges of stiffener 112 curve awayfrom the outer edges of substrate 104, which may detach or weaken theattachment of stiffener 112 to substrate 104. Furthermore, as shown inFIGS. 10B and 10C, the center region of stiffener 112, which has nounderlying support due to opening 604 in substrate 104, has become“bowl” shaped. This bowl shape for the center region of stiffener 112may cause damage to IC die 102. As IC die 102 is being forced downward(such as shown by arrows 1002) onto stiffener 112, a lack of support forthe center of IC die 102 exists in the center of the “bowl.” Hence, ICdie 102 may warp and/or develop one or more cracks due to the lack ofuniform support, causing IC die 102 to become inoperable.

[0076]FIG. 11 illustrates a cross-sectional view of an example IC diesupport structure that at least partially relieves stresses to anddeformation of elements of a BGA package, according to an embodiment ofthe present invention. As shown in FIG. 11, an IC die support structure1100 has been introduced to the mounting configuration shown in FIGS.10A-10C. IC die support structure 1100 resides in opening 604, betweenthe bottom surface of stiffener 112 and support surface 1000 (whenpresent). IC die support structure 1100 gives support to stiffener 112when IC die 102 is being mounted to stiffener 112, and during furtherassembly process operations on IC die 102. These include wire bondattachment and encapsulation processes, for example. As shown in FIG.11, force 1002 on IC die 102 causes relatively little or no deformationto stiffener 112. Hence, harm to stiffener 112 and IC die 102 is reducedor eliminated.

[0077] Furthermore, in embodiments, IC die support structure 1100 isremovably held in opening 604. As described below, IC die supportstructure 1100 may be removed from opening 604 after the relevantassembly process steps have been completed.

[0078] In the example of FIG. 11, IC die support structure 1100 issubstantially co-planar with substrate 104, and has substantially thesame rectangular shape as opening 604 (such as shown for opening 604 inFIG. 7). Furthermore, IC die support structure 1100 has a thickness thatis substantially equal to a thickness of substrate 104. In this manner,IC die support structure 1100 fits within opening 604 between stiffener112 and support surface 1000 (when present), and provides sufficientsupport to stiffener 112 during assembly operations. In alternativeembodiments, IC die support structure 1100 may have shapes other thanrectangular, including circular, for example. Furthermore, IC diesupport structure 1100 may have a shape different than that of opening604, including round or elliptical, and any polygon, for example. Stillfurther, IC die support structure 1100 may have other sizes, includinghaving greater or less thickness than substrate 104.

[0079] Example embodiments for holding IC die support structure 1100 inopening 604 are further described as follows. These examples areprovided for illustrative purposes, and the present invention is notlimited to these examples. These embodiments for holding IC die supportstructure 1100 may be used with or without support surface 1000 shown inFIG. 10A. Further mechanisms for holding IC die support structure 1100in opening 604 will be apparent to persons skilled in the relevantart(s) from the teachings herein.

[0080]FIG. 12 illustrates a top, plan view of substrate 104 having anexample IC die support structure 1100, according to an embodiment of thepresent invention. As shown in FIG. 12, substrate 104 has opening 604located in a central region of substrate 104. Opening 604 is open at thetop and bottom surfaces of substrate 104. Furthermore, IC die supportstructure 1100 is removably held in opening 604. IC die supportstructure 1100 is considered removably held in opening 604 because it isattached to an adhesive tape 1202, which is attached to, and may bedetached from substrate 104. Adhesive tape 1202 is attached to substrate104, and holds IC die support structure 1100 in opening 604. Aftercompleting relevant assembly process steps for a respective BGA package,adhesive tape 1202 may be detached from the corresponding substrate 104.Detaching adhesive tape 1202 from substrate 104 removes IC die supportstructure 1100 from opening 604. Adhesive tape 1202 may also be a rigidplanar carrier, such as a plate, etc. In such an embodiment, IC diesupport structure 1100 may be attached to the rigid planar carrier by anadhesive material, such as an adhesive tape, or by other mechanism,including removable and non-removable means.

[0081] IC die support structure 1100 as shown in FIG. 12 providessupport to stiffener 112 while IC die 102 is being mounted thereto, andwhile additional assembly processes are being executed on the respectiveBGA package. Adhesive tape 1202 may be any type of tape having anadhesive material on at least one surface. In embodiments, adhesive tape1202 may be of a size to attach a single IC die support structure 1100to a single substrate 104. In alternative embodiments, a single strip ofadhesive tape 1202 may be of a size to attach a plurality of IC diesupports 1100 to a plurality of substrates 104, such as in substratestrip 900. IC die support structure 1100 can be attached to adhesivetape 1202 at any time before, during, or after adhesive tape 1202 isattached to substrate 104.

[0082]FIG. 13 illustrates a view of substrate 104 with another exampleIC die support structure 1100, according to embodiments of the presentinvention. As shown in FIG. 13, substrate 104 has opening 604 located ina central region that is open at the top and bottom surfaces ofsubstrate 104. Furthermore, similarly to the embodiment shown in FIG.12, IC die support structure 1100 shown in FIG. 13 is removably held inopening 604. In FIG. 13, IC die support structure 1100 is consideredremovably held in opening 604 because it is held in opening 604 by abreakable stud or tab 1302. Tab 1302 may be broken to release IC diesupport structure 1100 from opening 604. Once IC die support structure1100 is released by breaking tab 1302, it may be physically removed ormay be allowed to drop from opening 604 on its own.

[0083] In embodiments, tab 1302 is made from a material external fromsubstrate 104 that is positioned in opening 604 to hold IC die supportstructure 1100. In another embodiment, tab 1302 and IC die supportstructure 1100 are portions of substrate 104 that remain in opening 604when opening 604 is formed in substrate 104. For example, tab 1302 andIC die support structure 1100 may be formed with opening 604 insubstrate 104 by cutting a non-continuous line in the shape of arectangle, or other shape, through substrate 104 in a center region. Thesubstrate material that is removed during the cutting process is removedfrom the gap formed between substrate 104 and IC die support structure1100. In such an embodiment, opening 604 may be formed around IC diesupport structure and tab 1302 by sawing, cutting, drilling, machining,by laser, and other ways.

[0084] IC die support structure 1100 as shown in FIG. 13 providessupport to stiffener 112 while IC die 102 is being mounted thereto, andwhile additional assembly processes are being executed on the respectiveBGA package. The example embodiment of FIG. 13 shows a single tab 1300located in a corner of opening 604, that removably holds IC die supportstructure 1100 in opening 604. FIGS. 14 and 15 illustrate views ofsubstrate 104 with IC die support structure 1100 removably held by oneor more tabs 1302, according to further embodiments of the presentinvention. FIG. 14 shows a first tab 1302 a removably holding IC diesupport structure 1100 in a first corner of opening 604, and a secondtab 1302 b removably holding IC die support structure 1100 in a secondcorner of opening 604. FIG. 15 shows tab 1302 removably holding IC diesupport structure 1100 to a middle area of an edge of opening 604. Anynumber of one or more tabs 1302 may be used to removably hold IC diesupport structure 1100 in opening 604. Furthermore, the one or more tabs1302 may be located anywhere in the corners or along the edges ofopening 604.

[0085] In embodiments, as described above, IC die support structure 1100may be a substrate portion formed from opening 604 of substrate 104, andhence be made from the same material as substrate 104. In furtherembodiments, IC die support structure 1100 can be made from a substratematerial that is the same as or different from that of substrate 104.These substrate materials include tape, plastic, and/or ceramicsubstrate materials. Furthermore, IC die support structure 1100 may bemade from a plastic material, such as BT and/or FR4, and/or a ceramic.IC die support structure 1100 can also be made from a metal, such ascopper, aluminum, tin, nickel, iron, other metals, andcombinations/alloys thereof. IC die support structure 1100 may be madefrom other materials as well.

[0086]FIG. 16 shows a flowchart 1600 providing steps for assembling aBGA package according to one or more embodiments of the presentinvention. Other operational and structural embodiments will be apparentto persons skilled in the relevant art(s) based on the followingdiscussion. These steps are described in detail below.

[0087] Flowchart 1600 begins with step 1602. In step 1602, a stiffeneris attached to a substrate that has a centrally located opening that isopen therethrough and has an integrated circuit (IC) die supportstructure removably held therein. For example, the stiffener isstiffener 112 and the substrate is substrate 104, which are attached toeach other, as shown in FIG. 11. As shown in FIG. 11, substrate 104 as acentrally located opening 604 that is open at the top and bottomsurfaces of substrate 104. Furthermore, opening 604 has IC die supportstructure 1100 removably positioned therein.

[0088] In step 1604, an IC die is mounted to a central region of thestiffener. For example, as shown in FIG. 11, IC die 102 is mounted tothe top surface of stiffener 112, in a central region that is oppositeto opening 604 in substrate 104.

[0089] In step 1606, the IC die support structure is removed from thecentrally located opening. For example, as described above, after one ormore assembly operations are performed on the BGA package, IC diesupport structure 1100 is removed from opening 604.

[0090] In embodiments, step 1604 includes the step where the IC diesupport structure is allowed to support the central region of thestiffener while the IC die is being mounted to the central region of thestiffener. For example, IC die support structure 1100 supports stiffener112 in the region adjacent to opening 604 in substrate 104 when assemblyoperations are performed that involve forces upon IC die 102, such asmounting IC die 102 to stiffener 112, attaching wire bonds 108/608, andapplying encapsulate 116.

[0091] In an embodiment, flowchart 1600 may include the additional stepwhere an adhesive tape is applied to the substrate to which the IC diesupport structure is attached so that the IC die support structure isremovably held within the centrally located opening. For example, theadhesive tape is adhesive tape 1202, as shown in FIG. 12. Adhesive tape1202 has IC die support structure 1100 attached thereto, and is appliedto substrate 104. IC die support structure 1100 is located and removablyheld in opening 604 by adhesive tape 1202.

[0092] In such an embodiment, step 1606 may include the step where theapplied adhesive tape is detached from the substrate to remove the ICdie support structure from the centrally located opening. For example,as described above, adhesive tape 1202 may be removed from substrate104. Because IC die support structure 1100 is attached to adhesive tape1202, IC die support structure 1100 is removed from opening 604 whenadhesive tape 1202 is detached.

[0093]FIG. 17A shows a flowchart 1700 providing steps for assembling aplurality of BGA packages according to one or more embodiments of thepresent invention. FIG. 17B provides additional optional steps,according to further embodiments of the present invention. Otheroperational and structural embodiments will be apparent to personsskilled in the relevant art(s) based on the following discussion. Thesesteps are described in detail below.

[0094] Flowchart 1700 begins with step 1702. In step 1702, a substratestrip that includes a plurality of substrates that each include acentrally located opening with an IC die support structure removablyheld therein is formed. For example, the substrate strip is substratestrip 900, as shown in FIG. 9. Substrate strip 900 includes a pluralityof substrates 104, that each include an opening 604. Similarly to thesingle substrate example of FIG. 11, stiffener strip 900 is formed sothat each substrate of the plurality of substrates 104 include an IC diesupport structure 1100 removably held therein.

[0095] In step 1704, a stiffener strip that includes a plurality ofstiffeners is attached to the substrate strip such that a first surfaceof each stiffener of the plurality of stiffeners is attached to a firstsurface of a corresponding substrate of the plurality of substrates. Forexample, the stiffener strip is stiffener strip 800, as shown in FIG. 8.As shown in FIG. 8, stiffener strip 800 includes a plurality ofstiffeners 112. Substrate strip 900 and stiffener strip 800 are attachedto each other to form a substrate strip/stiffener strip combination.

[0096] In step 1706, an IC die is mounted to a central region of asecond surface of each stiffener of the plurality of stiffeners. Forexample, similarly to that shown in FIG. 11 for a single stiffener, anIC die 102 is mounted to the top surface of each stiffener of theplurality of stiffeners 112 of stiffener strip 800, in a central regionthat is opposite to opening 604 in the respective substrate 104.

[0097] In step 1708, a bond pad of the IC die mounted to each stiffenerof the plurality of stiffeners is connected to a contact pad on thefirst surface of the corresponding substrate of the plurality ofsubstrates with a wire bond. For example, similar to the single IC dieexample of FIG. 6, a wire bond 108 may be used to connect a bond pad ofIC die 102 to a contact pad on the top surface of substrate 104, foreach IC die 102 and each corresponding substrate of the plurality ofsubstrates 104.

[0098] In step 1710, the IC die and the wire bond are encapsulated onthe second surface of each stiffener of the plurality of stiffeners. Forexample, as shown in FIG. 6 for a single IC die 102, an encapsulate 116may be applied to the BGA package to encapsulate IC die 102 and wirebonds 108/608 to the top surface of each stiffener of the plurality ofstiffeners 112.

[0099] In step 1712, the IC die support structure is removed from thecentrally located opening of each substrate of the plurality ofsubstrates. For example, as described above for a single IC die supportstructure 1100, after one or more assembly operations are performed onthe substrate strip/stiffener strip combinations, IC die supportstructure 1100 is removed from each opening 604.

[0100] In embodiments, one or more of steps 1706, 1708, and 1710 includethe step where the IC die support structure is allowed to support thecentral region of the stiffener during the respective step(s). Theassembly processes described above place respective forces upon IC die102. IC die support structure 1100 supports stiffener 112 during theseassembly process steps to prevent substantial deformation of stiffener112, and damage to IC die 102.

[0101] In an embodiment, step 1702 may include the step where anadhesive tape to which a plurality of IC die support structures areattached is applied to the substrate strip so that an IC die supportstructure of the plurality of IC die support structures is removablyheld within the centrally located opening of each substrate of theplurality of substrates. For example, the adhesive tape is adhesive tape1202, as shown for a single substrate 104 in FIG. 12. Adhesive tape 1202has IC die support structure 1100 for each opening 604 attached thereto,and is applied to substrate strip 900. An IC die support structure 1100is located and removably held in each opening 604 by adhesive tape 1202.Note that a single adhesive tape 1202 may removably hold all IC diesupport structures 1100, or a separate adhesive tape 1202 may be usedfor each IC die support structure 1100 in the substrate strip/stiffenerstrip combination.

[0102] In such an embodiment, step 1712 may include the step where theapplied adhesive tape is detached from the substrate strip to remove theIC die support structure held within the centrally located opening ofeach substrate of the plurality of substrates. For example, as describedabove, adhesive tape 1202 may be removed from the plurality ofsubstrates 104. Because each IC die support structure 1100 is attachedto adhesive tape 1202, each IC die support structure 1100 is removedfrom the respective opening 604.

[0103] In another embodiment, step 1702 may include the step where thecentrally located opening is formed in each substrate of the pluralityof substrates such that a substrate portion remains removably held inthe centrally located opening of each substrate of the plurality ofsubstrates by at least one substrate tab as the IC die supportstructure. For example, similarly to the single substrate examples shownin FIGS. 13-15, opening 604 may be formed for each substrate in theplurality of substrates 104 such that a portion of the substrate remainswithin each opening 604 as IC die support structure 1100. At least onesubstrate tab, such as tab 1302, removably holds IC die supportstructure 1100 in each opening 604.

[0104] In such an embodiment, step 1712 may include the step where theat least one substrate tab removably holding the substrate portion inthe centrally located opening of each substrate of the plurality ofsubstrates is broken to release the IC die support structure removablyheld within the centrally located opening of each substrate of theplurality of substrates. For example, as described above for a singlesubstrate 104, a respective tab 1302 may be broken to release IC diesupport structure 1100 in each opening 604, so that each IC die supportstructure 1100 may be removed.

[0105]FIG. 11B shows additional steps for flowchart 1700. Inembodiments, any number of one or more steps shown in FIG. 17B may becombined with flowchart 1700 shown in FIG. 17A. In an embodiment,flowchart 1700 may include the additional step of step 1714, as shown inFIG. 17B. In step 1714, a heat spreader is mounted to a central regionof the first surface of each stiffener of the plurality of stiffenersthrough the centrally located opening in each substrate of the pluralityof substrates. For example, as shown in FIG. 6 for a single BGA package,a heat spreader 602 may be coupled to each stiffener 112 through theopening 604 in the respective substrate 104 for each substrate/stiffenercombination in the substrate strip/stiffener strip combination, afterremoval of IC die support structures 1100.

[0106] In an embodiment, flowchart 1700 may include the additional stepof step 1716, as shown in FIG. 17B. In step 1716, a plurality of solderballs are attached to a second surface of each substrate of theplurality of substrates. For example, as shown in FIG. 6 for a singleBGA package, for each substrate of the plurality of substrates 104, aplurality of solder balls 106 may be applied to the bottom surface ofsubstrate 104.

[0107] In an embodiment, flowchart 1700 may include the additional stepof step 1718, as shown in FIG. 17B. In step 1718, a substrate/stiffenerstrip formed by attaching the stiffener strip to the substrate strip instep 1704 is singulated into a plurality of separate BGA packages. Forexample, after assembly processes have been performed on the stiffenerstrip/substrate strip combination, each stiffener/substrate combinationmay be separated from the stiffener strip/substrate strip combination toform a plurality of BGA packages. Sawing, cutting, machining, and otherprocesses may be used to perform the separation.

[0108] Further steps for the processes of flowcharts 1600 and 1700 shownin FIGS. 16, 17A, and 17B will be known to persons skilled in therelevant art(s) from the teachings herein.

[0109] Conclusion

[0110] While various embodiments of the present invention have beendescribed above, it should be understood that they have been presentedby way of example only, and not limitation. It will be apparent topersons skilled in the relevant art that various changes in form anddetail can be made therein without departing from the spirit and scopeof the invention. Thus, the breadth and scope of the present inventionshould not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A method of assembling a ball grid array (BGA)package, comprising: (A) attaching a first surface of a stiffener to afirst surface of a substrate that includes a centrally located openingthat is open at the first and a second surface of the substrate and hasan integrated circuit (IC) die support structure removably held therein;(B) after step (A), mounting an IC die to a central region of the secondsurface of the stiffener; and (C) after step (B), removing the IC diesupport structure from the centrally located opening.
 2. The method ofclaim 1, further comprising: (D) prior to step (A), applying to thesubstrate an adhesive tape to which the IC die support structure isattached so that the IC die support structure is removably held withinthe centrally located opening.
 3. The method of claim 2, wherein step(C) comprises: detaching the applied adhesive tape from the substrate toremove the IC die support structure from the centrally located opening.4. The method of claim 1, further comprising: (D) after step (B) andprior to step (C), connecting a bond pad of the IC die to a contact padon the first surface of the substrate with a wire bond.
 5. The method ofclaim 1, further comprising: (D) after step (B) and prior to step (C),encapsulating the IC die on the second surface of the stiffener.
 6. Themethod of claim 1, further comprising: (D) prior to step (A), formingthe centrally located opening in the substrate such that a portion ofthe substrate remains removably held therein by at least one substratetab wherein said substrate portion acts as the IC die support structure.7. The method of claim 6, wherein step (C) comprises: breaking the atleast one substrate tab to release the IC die support structure from thecentrally located opening.
 8. The method of claim 1, wherein step (B)comprises: allowing the IC die support structure to support a centralregion of the first surface of the stiffener while the IC die is beingmounted to the central region of the second surface of the stiffener. 9.The method of claim 4, wherein step (D) comprises: allowing the IC diesupport structure to support a central region of the first surface ofthe stiffener while the wire bond is being attached to the bond pad ofthe IC die.
 10. The method of claim 5, wherein step (D) comprises:allowing the IC die support structure to support a central region of thefirst surface of the stiffener while the IC die is being encapsulated.11. A method of assembling a plurality of ball grid array (BGA)packages, comprising: (A) forming a substrate strip that includes aplurality of substrates that each include a centrally located openingwith an integrated circuit (IC) die support structure removably heldtherein; (B) attaching to the substrate strip a stiffener strip thatincludes a plurality of stiffeners such that a first surface of eachstiffener of the plurality of stiffeners is attached to a first surfaceof a corresponding substrate of the plurality of substrates; (C) afterstep (B), mounting an IC die to a central region of a second surface ofeach stiffener of the plurality of stiffeners; (D) after step (C),connecting a bond pad of the IC die mounted to each stiffener of theplurality of stiffeners to a contact pad on the first surface of thecorresponding substrate of the plurality of substrates with a wire bond;(E) encapsulating the IC die and the wire bond on the second surface ofeach stiffener of the plurality of stiffeners; and (F) removing the ICdie support structure from the centrally located opening of eachsubstrate of the plurality of substrates.
 12. The method of claim 11,wherein step (A) comprises: applying to the substrate strip an adhesivetape to which a plurality of IC die support structures are attached sothat an IC die support structure of the plurality of IC die supportstructures is removably held within the centrally located opening ofeach substrate of the plurality of substrates.
 13. The method of claim12, wherein step (F) comprises: detaching the applied adhesive tape fromthe substrate strip to remove the IC die support structure held withinthe centrally located opening of each substrate of the plurality ofsubstrates.
 14. The method of claim 11, wherein step (A) comprises:forming the centrally located opening in each substrate of the pluralityof substrates such that a substrate portion remains removably held inthe centrally located opening of each substrate of the plurality ofsubstrates by at least one substrate tab as the IC die supportstructure.
 15. The method of claim 14, wherein step (F) comprises:breaking the at least one substrate tab removably holding the substrateportion in the centrally located opening of each substrate of theplurality of substrates to release the IC die support structureremovably held within the centrally located opening of each substrate ofthe plurality of substrates.
 16. The method of claim 11, furthercomprising: (G) mounting a heat spreader to a central region of thefirst surface of each stiffener of the plurality of stiffeners throughthe centrally located opening in each substrate of the plurality ofsubstrates.
 17. The method of claim 11, further comprising: (G)attaching a plurality of solder balls to a second surface of eachsubstrate of the plurality of substrates.
 18. The method of claim 11,further comprising: (G) after step (F), singulating asubstrate/stiffener strip formed by attaching the stiffener strip to thesubstrate strip in step (B) into a plurality of separate BGA packages.19. A substrate with IC die support apparatus for use during assembly ofa ball grid array (BGA) package, comprising: a substantially planarsubstrate having opposing first and second surfaces, and having anopening through said substrate in a central region that is open at saidfirst surface and said second surface; and an IC die support structureremovably held in said opening.
 20. The apparatus of claim 19, whereinsaid IC die support structure is substantially co-planar with saidsubstrate, and said IC die support structure has a thickness that issubstantially equal to a thickness of said substrate.
 21. The apparatusof claim 19, wherein the IC die support structure is a substrateportion, further comprising: at least one breakable substrate tab thatremovably holds said IC die support structure in said opening; wherebysaid IC die support structure is released from said opening by breakingsaid at least one breakable substrate tab.
 22. The apparatus of claim21, wherein said opening, said substrate portion, and said at least onebreakable substrate tab are formed in the substrate by cutting anon-continuous line substantially in the shape of a rectangle throughsaid substrate in said central region.
 23. The apparatus of claim 19,further comprising: an adhesive tape applied to said IC die supportstructure and said first surface of said substrate to removably holdsaid IC die support structure within said opening; whereby said IC diesupport structure is removed from said opening by detaching saidadhesive tape from said substrate.
 24. The apparatus of claim 19,wherein said IC die support structure comprises a substrate material.25. The apparatus of claim 19, wherein said IC die support structurecomprises at least one of a BT and FR4.
 26. The apparatus of claim 19,wherein said IC die support structure comprises a ceramic.
 27. Theapparatus of claim 19, wherein said IC die support structure comprisesat least one metal.
 28. The apparatus of claim 19, wherein said IC diesupport structure comprises a metal alloy.
 29. The apparatus of claim19, wherein said IC die support structure comprises a plastic.
 30. Theapparatus of claim 19, wherein said IC die support structure has a shapesubstantially equal to a shape of said opening.
 31. The apparatus ofclaim 30, wherein said IC die support structure is substantiallyrectangular shaped.